Can a narcissist ever get better and, if not, how should his partner end a relationship with him?
A Narcissistic Personality Disorder is a systemic, all-pervasive condition, very much like pregnancy: either you have it or you don't. Once you have it, you have it day and night, it is an inseparable part of the personality, a recurrent set of behaviour patterns.
Recent research shows that there is a condition, which might be called "Transient or Temporary or Short-Term Narcissism" as opposed to "The Real Thing - The Narcissistic Personality Disorder, (NPD)" [Roningstam, 1996]. The phenomenon of "reactive narcissistic regression" is well known: people regress to a transient narcissistic phase in reaction to a major life crisis which threatens their mental composure.
There are narcissistic touches in every personality and in this sense, all of us are narcissists to some extent. But this is a far cry from the NPD pathology.
One bit of good news: no one knows why, but, in certain cases, though rarely, with age (in one's forties), the disorder seems to decay and, finally, stay on in the form of a subdued mutation of itself. This does not universally occur, though.
Should a partner stay on with a narcissist in the hope that his disorder will be ameliorated by ripe age? This is a matter of value judgement, preferences, priorities, background, emotions and a host of other "non-scientific" matters. There could be no one "right" answer. It would seem that the only valid criterion is the partner's well-being. If he or she feels bad in a relationship (and no amount of self-help or of professional help changes that) - then looking for the exit door sounds like a viable and healthy strategy.
This raises the second part of the question: a relationship with a narcissist is of dependence, even symbiosis. Moreover, the narcissist is a superb emotional manipulator and extortionist. In some cases, there is real threat to his mental stability. Even "demonstrative" (failed) suicide cannot be ruled out in the repertory of narcissistic reactions to abandonment. And even a modest amount of residual love harboured by the narcissist's partner makes the separation very difficult for him or her.
But there is a magic formula.
A narcissist is with his partner because he regards IT as a Source of Narcissistic Supply. He values the partner as such a source. Put differently: the minute that the partner ceases to supply him with what he needs - he loses all interest in IT. (I use IT judiciously - the narcissist objectifies his partners, treats them as he would inanimate objects.)
The transition from over-valuation (bestowed upon Sources of Narcissistic Supply) to devaluation (reserved for other mortals) is so swift that it is likely to inflict pain upon the narcissist's partner, even if he previously prayed for the narcissist to depart and leave him alone. The partner is the narcissist's pusher and the drug that he is proffering is stronger than any other drug because it sustains the narcissist's very essence (his False Self).
Without Narcissistic Supply the narcissist disintegrates, crumbles and shrivels - very much as vampires do in horror movies when exposed to sunlight.
Here lies the partner's salvation. An advice to you: if you wish to sever your relationship with the narcissist, stop providing him with what he needs. Do not adore, admire, approve, applaud, or confirm anything that he does or says. Disagree with his views, belittle him (or put him in perspective and proportion), compare him to others, tell him that he is not unique, criticise him, make suggestions, offer help. In short, deprive him of that illusion which holds his personality together.
The narcissist is a delicately attuned piece of equipment. At the first sign of danger to his inflated, fantastic and grandiose self - he will disappear on you.